What causes a toddler's leg to turn inward and bow, possibly due to hip dysplasia or femoral anteversion?

Causes of Inward Leg Turning and Bowing in Toddlers

The primary causes of a toddler's leg turning inward and bowing include physiologic variants such as internal tibial torsion, femoral anteversion, and developmental dysplasia of the hip (DDH), with most cases being normal developmental variations that resolve spontaneously with growth. 1

Common Causes

Physiologic Variants

• In-toeing in toddlers is commonly caused by:

  • Internal tibial torsion (inward rotation of the tibia)
  • Femoral anteversion (excessive forward rotation of the femoral neck)
  • Talar torsion (medial deviation of the talus neck)
  • Metatarsus adductus (inward turning of the forefoot) 1

• Bowing of legs (genu varus) is often physiologic in toddlers and typically resolves spontaneously as the child grows 2

Developmental Dysplasia of the Hip (DDH)

• DDH represents a spectrum of abnormalities from hip instability to frank dislocation 3
• Key physical examination findings include:
  • Limited hip abduction (most important finding in children over 2-3 months)
  • Asymmetric buttock creases
  • Leg length discrepancy 3

Diagnostic Considerations

Physical Examination

• For children under 2-3 months: Barlow and Ortolani tests can detect unstable hips 3
• For older children: Limited hip abduction becomes the most important finding as the hip capsule tightens with age 3
• Assess for asymmetric buttock creases and leg length discrepancy 3

Imaging

• Ultrasound is the preferred imaging modality for infants under 4-6 months 3

  • Two main techniques:
    • Graf method: Static assessment of acetabular morphology using alpha angle measurements
    • Harcke method: Dynamic assessment that visualizes hip stability during stress maneuvers 3

• Radiography becomes more useful after ossification of the femoral head (typically after 4-6 months) 3

  • Key measurements include:
    • Acetabular index (normally 30° in newborns, decreases with age)
    • Position of femoral head relative to Hilgenreiner and Perkin lines
    • Shenton's line continuity 3

• MRI can be valuable for assessing both femoral and acetabular anteversion, particularly in children of walking age (12-48 months) 4

Natural History and Management

Physiologic Variants

• Most cases of in-toeing and bowing resolve spontaneously:
  • Internal tibial torsion typically resolves before age 7
  • Physiologic bowing usually corrects with growth and maturation of lower extremities 1, 2

Persistent Deformities

• A small percentage of cases may persist if untreated:
  • Femoral anteversion becomes fixed by approximately age 8
  • Internal tibial torsion persists in about 8% of cases 1

Treatment Considerations

• Early intervention may be warranted for:

  • Severe metatarsus adductus (serial casting for infants under 8 months)
  • Significant internal tibial torsion (bracing for infants up to 18 months if deviation exceeds 10 degrees)
  • Genu varus exceeding age-appropriate norms (Danish night-splint may prevent progression to Blount's disease) 1, 5

• For DDH, treatment depends on severity and age at diagnosis:

  • Early detection is crucial as late presentation increases the likelihood of requiring complex treatment and surgical intervention 3
  • Untreated DDH can lead to early degenerative joint disease and may necessitate total hip arthroplasty later in life 3

Important Considerations

• Age is a critical factor in determining the appropriate treatment approach 5
• Early, gentle conservative therapy should be considered for appropriate cases 5
• The American Academy of Pediatrics recommends selective screening for DDH in children with risk factors or concerning physical examination findings 3
• Most borderline "abnormal" hips during infancy represent physiologic immaturity, with 60-80% identified by physical examination and over 90% identified by ultrasound normalizing spontaneously 3